1. Field of the Invention
The embodiments of the invention generally relate to manufacturing execution systems and, more particularly, to an improved dispatch system, method and computer program product for monitoring and controlling the flow of articles of manufacture through the fabrication process such that tool usage is evenly distributed throughout the fabrication process.
2. Description of the Related Art
In automated manufacturing systems, manufacturing execution systems (MES) are typically used to monitor and control all aspects of product fabrication and production. For example, the MES can be adapted to control collection and storage of data, manage work orders, manage and control manufacturing processes, monitor and correct manufacturing processes, manage inventory, etc. In order to accomplish these tasks, the MES can be integrated with various other systems.
For example, in order to manage process flow, the MES can be integrated with a run-time dispatch system. Specifically, manufacturing processes, such as wafer-level integrated circuit (IC) fabrication, generally involve a large number of process steps (e.g., film depositing, photolithographic patterning, pattern transferring (i.e., etching), polishing, annealing, dopant implanting, etc.). During any one of theses steps, multiple tools are often available for use. For example, one or more deposition tools may be available, one or more lithography tools may be available, one or more etching tools may be available, etc. Additionally, within each of these tools, multiple process chambers may be available. Thus, for a given IC product design, each lot of wafers may be processed by different tools at different steps in the manufacturing process. Additionally, within each lot, each wafer may be processed by different chambers within a given tool. A run-time dispatch system can be integrated with the MES in order to schedule the order in which individual lots will be processed and also to assign available tools to particular lots at each process step. Typically, such dispatch systems prioritize scheduling and tool assignment based on various parameters (e.g., priority of jobs, tool availability, etc.). If no one lot has priority and all tools are available, dispatch (i.e., scheduling and tool assignment) is often arbitrary.
Given the number of process steps, the number of tools available at each step and the number of chambers available in each tool, the total number of possible combinations of process steps and tools which may be assigned by the dispatch system to any given job is very large. If the number of different chambers available in each tool is also factored in, the number of possible process combinations becomes even greater. This large number of process combinations allows each lot to flow smoothly through a fabrication facility. Unfortunately, the same large number of possible process combinations subsequently makes it difficult to identify a faulty tool or chamber, when a manufacturing defect is detected during processing.